Snowmobile

ABSTRACT

The present specification relates to a snowmobile. The upper arm includes two proximal portions connected to the vehicle frame and the upper arm extends outwardly from the two proximal portions in the vehicle width direction and the upper arm is connected to the knuckle. The two proximal portions are rotatable so that the knuckle and the skis can move up and down relative to the vehicle frame. The axis Ax2, passing through the rotation center C2 of the two proximal portions of the upper arm, goes through a position of the rotation center of the secondary shaft or through a position above the rotation center of the secondary shaft. This structure can reduce the force acting on the vehicle body frame via the upper arm and prevent an increase in the force.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese applicationJP2016-018164 filed on Feb. 2, 2016, the entire content of which ishereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present specification relates to a support structure of skis insnowmobiles.

2. Description of the Related Art

As disclosed in US Patent Application Publication No. 2013/0032417,snowmobiles have upper arms and lower arms for supporting the left andright skis. The upper arm and the lower arm include proximal portionsconnected to the front portion of the vehicle frame. The upper arm andthe lower arm include distal ends connected to a knuckle. The ski isconnected to the lower end of the knuckle. The proximal portion of theupper arm and the proximal portion of the lower arm are rotatablyconnected to the vehicle frame so that the ski and the knuckle can moveup and down relative to the vehicle frame.

When the ski moves up and down, a force acting on the ski from the snowsurface is transmitted to the vehicle frame via the knuckle and theupper arm. At this time, the knuckle works like a lever, and theconnecting point between the knuckle and the lower arm works as thefulcrum of the lever. Magnitude of the force acting on the vehicle framethrough the upper arm depends on the position (height) of the connectingportion, which is the fulcrum, between the knuckle and the lower arm.

Snowmobiles include a front portion of the vehicle frame that supportsthe lower arm and the upper arm, and include a drive system, includingan engine, located rearward of the front portion of the vehicle frame.The engine includes a crank shaft. The drive system further includes asecondary shaft coupled with the crank shaft through a belt or a gearand receives drive force from the crank shaft. The rotation of thesecondary shaft is transmitted to a driving rotating member that isdisposed inside and engaged with the track belt. In most snowmobiles,the crank shaft is located in the lower portion of the engine and thesecondary shaft is located higher than the crank shaft.

SUMMARY OF THE INVENTION

As described above, the magnitude of the force acting on the vehicleframe through the upper arm depends on the position (height) of thefulcrum that is the connecting portion between the knuckle and the lowerarm. In order to reduce the force acting on the vehicle frame throughthe upper arm, it is preferable that the connecting position between thelower arm and knuckle is close to the ski. That is, it is preferablethat the position of the lower arm is low. However, the lower arm at thelow position causes a lot of snow to hit it when the vehicle travels indeep snow, resulting in an increase in running resistance.

One of the objects of the present specification is to provide asnowmobile that can reduce the force acting on the vehicle frame throughthe upper arm and can prevent the force from being increased.

A snowmobile according to a first embodiment described in the presentspecification includes: a vehicle frame including a ski support frame ina front portion of the vehicle frame; a ski disposed outwardly in avehicle width direction from the ski support frame; a knuckle includinga lower end having the ski connected thereto; an upper arm including aproximal portion connected to the ski support frame and extendingoutwardly in the vehicle width direction from the proximal portion toconnect to the knuckle, the proximal portion being rotatable so that theski and the knuckle can move up and down relative to the ski supportframe; a lower arm disposed below the upper arm, including a proximalportion connected to the ski support frame, and extending outwardly inthe vehicle width direction from the proximal portion to connect to theknuckle, the proximal portion being rotatable so that the ski and theknuckle can move up and down relative to the ski support frame; and adrive system including an engine and a secondary shaft, the engine beingdisposed rearward of the ski support frame and including a crank shaft,the secondary shaft being located higher than the crank shaft andconfigured to receive a drive force from the crank shaft. The proximalportion of the upper arm has a rotational center and an axis passingthrough the rotational center, and the axis goes through a position of arotational center of the secondary shaft in side view of a vehicle body,or through a position above the rotational center of the secondary shaftin side view of the vehicle body. Such a snowmobile can reduce the forceacting on the vehicle frame through the upper arm and can prevent theforce from being increased.

A snowmobile according to a second embodiment described in the presentspecification includes: a vehicle frame including a ski support frame ina front portion of the vehicle frame; a ski disposed outwardly in avehicle width direction from the ski support frame; a knuckle includinga lower end having the ski connected thereto; an upper arm including aproximal portion connected to the ski support frame and extendingoutwardly in the vehicle width direction from the proximal portion toconnect to the knuckle, the proximal portion being rotatable so that theski and the knuckle can move up and down relative to the ski supportframe; a lower arm disposed below the upper arm, including a proximalportion connected to the ski support frame, and extending outwardly inthe vehicle width direction from the proximal portion to connect to theknuckle, the proximal portion being rotatable so that the ski and theknuckle can move up and down relative to the ski support frame; and adrive system including an engine and a secondary shaft, the engine beingdisposed rearward of the ski support frame and including a crank shaft,the secondary shaft being located higher than the crank shaft andconfigured to receive a drive force from the crank shaft. The heightfrom a lower end of the engine to the proximal portion of the upper armis 300 mm or more in a side view of a vehicle body. In this snowmobile,the upper arm is positioned higher than that of conventionalsnowmobiles. As a result, this snowmobile can reduce the force acting onthe vehicle frame through the upper arm and can prevent the force frombeing increased.

A snowmobile according to a third embodiment described in the presentspecification includes: a vehicle frame including a ski support frame ina front portion of the vehicle frame; a ski disposed outwardly in avehicle width direction from the ski support frame; a knuckle includinga lower end having the ski connected thereto; an upper arm including aproximal portion connected to the ski support frame and extendingoutwardly in the vehicle width direction from the proximal portion toconnect to the knuckle, the proximal portion being rotatable so that theski and the knuckle can move up and down relative to the ski supportframe; a lower arm disposed below the upper arm, including a proximalportion connected to the ski support frame, and extending outwardly inthe vehicle width direction from the proximal portion to connect to theknuckle, the proximal portion being rotatable so that the ski and theknuckle can move up and down relative to the ski support frame; and adrive system including an engine and a secondary shaft, the engine beingdisposed rearward of the ski support frame and including a crank shaft,the secondary shaft being located higher than the crank shaft andconfigured to receive a drive force from the crank shaft. The knucklehas a distance of 430 mm or more between the lower end of the knuckleand an upper end of the knuckle. In such a snowmobile, the upper arm ispositioned higher than that of conventional snowmobiles. As a result,this snowmobile can reduce the force acting on the vehicle frame throughthe upper arm and can prevent the force from being increased.

In the snowmobile described in any one of the above embodiments, atleast a portion of the proximal portion of the upper arm may bepositioned higher than the rotational center of the secondary shaft.

In the snowmobile described in any one of the above embodiments, each ofthe upper arm and the lower arm may include a distal end connected tothe knuckle, and an intersection point at which the axis passing throughthe rotational center of the proximal portion of the upper arm crossesan imaginary plane may be located higher than the rotational center ofthe secondary shaft. In the above, the imaginary plane is defined as aplane that passes through the distal ends of the lower arm and the upperarm and is parallel to the vehicle width direction.

In the snowmobile described in any one of the above embodiments, theupper arm may include a distal end connected to the knuckle, and theheight from a lower end of the ski to the distal end of the upper armmay be greater than the height from the lower end of the ski to therotational center of the secondary shaft.

In the snowmobile described in any one of the above embodiments, theknuckle may include a first connecting portion having the upper armconnected thereto and a second connecting portion having the lower armconnected thereto, and the second connecting portion may be located atsubstantially the same height as a middle position between the firstconnecting portion and the lower end of the knuckle or located lowerthan the middle position.

In the snowmobile described in any one of the above embodiments, theproximal portion of the lower arm may be located higher than arotational center of the crank shaft of the engine. This can prevent alot of snow from hitting the lower arm.

The snowmobile described above may further include a suspensionincluding an upper end connected to the ski support frame and a lowerend connected to the lower arm. In addition, the upper end of thesuspension may be located higher than the rotational center of thesecondary shaft. This arrangement of the suspension can prevent theangle between the suspension and the lower arm from decreasing when theposition of the lower arm is raised.

In the snowmobile described in any one of the above embodiments, thevehicle frame may include an engine support frame supporting the engine,where the ski support frame is shifted upward relative to the enginesupport frame.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an exemplary snowmobile according to theembodiments. In this figure, the vehicle body cover that constitutes theexterior of the snowmobile is removed.

FIG. 2A is a side view showing the front portion of the vehicle body. Inthis figure, the body cover that constitutes the exterior of thesnowmobile is removed.

FIG. 2B is a side view illustrating a positional relationship among thearms supporting the skis, suspensions, and the engine.

FIG. 3 is a plan view showing the vehicle frame, the left ski, and thesuspension.

FIG. 4 is a front view showing the vehicle frame, the right and leftskis, and the suspensions.

FIG. 5 is a perspective view showing the vehicle frame, the left ski,and the suspension.

DETAILED DESCRIPTION OF THE INVENTION

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. As used herein, the singularforms “a,” “an,” and “the” are intended to include the plural forms aswell as the singular forms, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, operations, elements, and/or components,but do not preclude the presence or addition of one or more otherfeatures, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by onehaving ordinary skill in the art to which this invention belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

In describing the invention, it will be understood that a number oftechniques and are disclosed. Each of these has individual benefit andeach can also be used in conjunction with one or more, or in some casesall, of the other disclosed techniques. Accordingly, for the sake ofclarity, this description will refrain from repeating every possiblecombination of the individual techniques in an unnecessary fashion.Nevertheless, the specification and claims should be read with theunderstanding that such combinations are entirely within the scope ofthe invention and the claims.

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be evident, however, toone skilled in the art that the present invention may be practicedwithout these specific details.

The present disclosure is to be considered as an exemplification of theinvention, and is not intended to limit the invention to the specificembodiments illustrated by the figures or description below.

The various embodiments will be described by referencing the appendedfigures. FIG. 1 is a side view of one snowmobile embodiment. FIG. 2A isa side view showing the front portion of the vehicle body. In FIGS. 1and 2A, the vehicle body cover that constitutes the exterior of thesnowmobile is removed. FIG. 2B is a side view illustrating a positionalrelationship among the arms 42 and 43 supporting the skis 41R and 41L,suspensions 45, and the engine 11. FIG. 3 is a plan view showing thevehicle frame 30, the left ski 41L, and the suspension 45. FIG. 4 is afront view showing the vehicle frame 30, the right and left skis 41R and41L, and the suspensions 45. FIG. 5 is a perspective view showing thevehicle frame 30, the left ski 41L, and the suspension 45.

In the following description, Y1 and Y2 illustrated in the abovedescribed in drawings indicate forward and rearward directions,respectively. Further, Z1 and Z2 indicate upward and downwarddirections, respectively. X1 and X2 indicate rightward and leftwarddirections, respectively.

As shown in FIG. 1, the snowmobile 1 includes a drive system for drivingthe track belt 16. The drive system includes an engine 11, atransmission 12, a secondary shaft 13 and a track belt drive shaft 14.

The engine 11 includes a crank case 11 d (see FIG. 3) accommodating thecrankshaft 11 a. As shown in FIG. 2A, the engine 11 includes a cylinderblock 11 b attached to the crank case 11 d and a cylinder head 11 cattached to the cylinder block 11 b. The cylinder block 11 b has acylinder formed therein. The cylinder head 11 c has an intake passageand an exhaust passage formed therein that are connected to thecombustion chamber inside the cylinder. In the example of snowmobile 1,the crank case 11 d is located further rearward than a ski support frame31 (see FIG. 1) constituting the front portion of the vehicle frame 30(the ski support frame 31 will be described later). The cylinder block11 b and the cylinder head 11 c are attached to the upper side of thecrank case 11 d and arranged such that the axis line of the cylinder isinclined backward. Accordingly, the engine 11 does not overlap with thelater-described arms 42 and 43 supporting the skis 41R and 41L in sideview of the vehicle body. The posture of engine 11 is not limited to theexample of snowmobile 1. For example, a part of the engine 11 mayoverlap with the arms 42 and 43 in side view of the vehicle body.

The transmission 12 is, for example, a continuously variabletransmission, and includes a driving pulley 12 a receiving a torque froma crank shaft 11 a and a driven pulley 12 b receiving a torque from thedriving pulley 12 a, as shown in FIG. 2A. A belt 12 c (see FIG. 1) iswound around the pulleys 12 a and 12 b for transmitting the torque ofthe driving pulley 12 a to the driven pulley 12 b. In the example ofsnowmobile 1, the driving pulley 12 a is mounted on the crank shaft 11a. The driven pulley 12 b is mounted on the secondary shaft 13. Thesecondary shaft 13 is located further rearward and higher than the crankshaft 11 a. The driving pulley 12 a and the driven pulley 12 b aremounted, for example, at the end of the crank shaft 11 a and the end ofthe secondary shaft 13, respectively. As shown in FIG. 3, the drivingpulley 12 a and the driven pulley 12 b are located, for example,outwardly in the vehicle width direction from a later-described enginesupport frame 32 (pulleys 12 a and 12 b are located leftward in thevehicle width direction from the engine support frame 32, in the exampleof snowmobile 1). Unlike the example of snowmobile 1, the driving pulley12 a and the driven pulley 12 b may be located inside the engine supportframe 32 in the vehicle width direction.

The arrangement of the transmission 12 is not limited to the example ofsnowmobile 1. For example, the driving pulley 12 a may be mounted on aprimary shaft different from the crank shaft 11 a. In still anotherexample, the transmission 12 is not a continuously variabletransmission. In the present specification, “secondary shaft” means ashaft on which the driven member of the transmission 12 is mounted. Thatis, for the snowmobile including the continuously variable transmissionas the transmission 12, the secondary shaft means the shaft on which thedriven pulley 12 b is mounted. For a snowmobile including a gear typetransmission as the transmission 12, the secondary shaft means a shafton which the driven gear of the transmission 12 is mounted (the drivengear means a gear that engages with a driving gear mounted on theprimary shaft).

The track belt drive shaft 14 is connected to the secondary shaft 13through a belt, a chain, and the like, and receives a torque from thesecondary shaft 13 to rotate it. As shown in FIG. 1, the track beltdrive shaft 14 has a sprocket 14 b mounted thereon that is locatedinside the track belt 16 and is engaged with the track belt 16. Guidewheels 15 a, 15 b and 15 c for guiding the track belt 16 and a sliderail 17 for guiding the track belt 16 are further arranged inside thetrack belt 16. The slide rail 17 presses the track belt 16 toward thesnow surface.

As shown in FIG. 1, the seat 8 is disposed above the track belt 16. Thesnowmobile 1 includes, in front of the seat 8, a steering handle 21 forthe driver to steer the skis 41R and 41L. In addition, the snowmobile 1includes a steering column 22 extending diagonally downward and forwardfrom the center portion of the steering handle 21. The steering handle21 is connected to the skis 41R and 41L through the steering column 22,a tie rod 24 (see FIG. 4) and a knuckle 44 which will be describedlater. The snowmobile 1 includes a fuel tank 9 for storing the fuel forthe engine 11. As shown in FIG. 1, the fuel tank 9 is disposed, forexample, between the steering column 22 and the seat 8. In the exampleof snowmobile 1, the engine 11 is located below the steering column 22and the fuel tank 9.

The snowmobile 1 includes the right ski 41R and the left ski 41L (seeFIG. 4). As shown in FIG. 2A, the vehicle frame 30 of the snowmobile 1includes a ski support frame 31. The skis 41R and 41L are disposedoutwardly in the vehicle width direction from the ski support frame 31.That is, the right ski 41R is disposed in the right direction of the skisupport frame 31, and the left ski 41L is disposed in the left directionof the ski support frame 31. The snowmobile 1 includes an upper arm 42and a lower arm 43 located below the upper arm 42. The upper arm 42includes proximal portions 42 a and 42 b connected to the ski supportframe 31 and extends outwardly from the proximal portions 42 a and 42 bin the vehicle width direction. The lower arm 43 includes proximalportions 43 a and 43 b connected to the ski support frame 31 and extendsoutwardly from the proximal portions 43 a and 43 b in the vehicle widthdirection. That is, the snowmobile 1 includes an upper arm 42 and alower arm 43 that are located to the right of the ski support frame 31and that connect the ski support frame 31 and the right ski 41R. Inaddition, the snowmobile 1 includes a left arm 42 and a lower arm 43that are located to the left of the ski support frame 31 and thatconnect the ski support frame 31 and the left ski 41L. The distal end 42p of the upper arm 42 and the distal end 43 p of the lower arm 43 areconnected to the knuckle 44. The skis 41R and 41L are connected to thelower ends 44 f of the knuckles 44. In the present specification, “skisupport frame” means a portion of the vehicle frame 30 to which theproximal portions 43 a and 43 b of the lower arm 43 and the proximalportions 42 a and 42 b of the upper arm 42 are connected. The skisupport frame 31 may be integrally formed with another part of thevehicle frame 30 (for example, an engine support frame 32 to bedescribed later). Alternatively, the ski support frame 31 may be formedseparately from other portions of the vehicle frame 30 and may be fixedto the other portion by a fixing means such as bolts or welding.

In the example of snowmobile 1, as shown in FIG. 4, the proximalportions 43 a and 43 b of the lower arm 43 are located closer to thecenter in the vehicle width direction than the proximal portions 42 aand 42 b of the upper arm 42. On the other hand, in the left-rightdirection (the vehicle width direction), the position of the distal endof the upper arm 42 is substantially equal to the position of the distalend of the lower arm 43. Therefore, the lower arm 43 is longer than theupper arm 42.

The proximal portions 42 a, 42 b, 43 a and 43 b of the arms 42 and 43are rotatably connected to the ski support frame 31. That is, theproximal portions 42 a, 42 b, 43 a and 43 b of the arms 42 and 43 areconnected to the ski support frame 31 so that the arms 42 and 43 canmove up and down about the proximal portions 42 a, 42 b, 43 a and 43 b.These connections of the arms 42 and 43 allow the knuckle 44 and theskis 41R and 41L to move up and down relative to the vehicle frame 30.As shown in FIG. 3, the upper arm 42 includes a front rod 42 m and arear rod 42 n located behind the front rod 42 m. The lower arm 43includes a front rod 43 m and a rear rod 43 n located behind the frontrod 43 m. The proximal portion 42 a of the front rod 42 m, the proximalportion 42 b of the rear rod 42 n, the proximal portion 43 a of thefront rod 43 m, and the proximal portion 43 b of the rear rod 43 n areconnected to the ski support frame 31. The proximal portions 42 a, 42 b,43 a and 43 b are provided with shafts. The shafts of the proximalportions 42 a, 42 b, 43 a, and 43 b are supported by the arm connectingportions 31 a, 31 b, 31 c, and 31 d (see FIGS. 2A and 5) formed on thelateral side of the ski support frame 31, respectively.

In the example of snowmobile 1, the ski support frame 31 is formed of aplurality of panels. For example, as shown in FIG. 4, the ski supportframe 31 includes left and right side panels 31 g located away from eachother in the vehicle width direction (left-right direction), and a frontpanel 31 f fixed to the front edges of the left and right side panels 31g. The arm connecting portions 31 a, 31 b, 31 c, and 31 d supporting thearms 42 and 43 may be fixed to the panels 31 f and 31 g by welding, orintegrally formed with the panels 31 f and 31 g.

As shown in FIG. 4, in the example of snowmobile 1, the side panel 31 gis obliquely arranged toward the center of the vehicle width direction.The side panel 31 g extends from the portion having the proximalportions 42 a and 42 b of the upper arm 42 connected thereto (that is,the portion having the arm connecting portions 31 a and 31 b formedthereon) to the portion having the proximal portions 43 a and 43 b ofthe lower arm 43 connected thereto (that is, the portion having the armconnecting portions 31 c and 31 d formed thereon). The width of thefront panel 31 f in the left-right direction gradually decreasesdownward in conformity with the inclination of the left and right sidepanels 31 g. The structure of the ski support frame 31 is not limited tothe example described here. For example, the ski support frame 31 may becomposed of a plurality of pipes. In this case, the arm connectingportions 31 a, 31 b, 31 c, and 31 d may be fixed to the pipes.

The upper arm 42 is substantially triangular in a plan view thereof, andthe two rods 42 m and 42 n of the upper arm 42 are connected to a commonend (that is, the distal end 42 p of the upper arm 42). The lower arm 43is also substantially triangular in a plan view thereof, and the tworods 43 m and 43 n of the lower arm 43 are connected to a common end(that is, the distal end 43 p of the lower arm 43). The distal end 42 pof the upper arm 42 is connected to the knuckle 44 with a ball joint,for example, so that the angle between the knuckle 44 and the upper arm42 can change. Likewise, the distal end 43 p of the lower arm 43 isconnected to the knuckle 44 with a ball joint, for example, so that theangle between the knuckle 44 and the lower arm 43 can change.

As shown in FIG. 2A, the engine 11 is disposed rearward of the skisupport frame 31. The vehicle frame 30 includes an engine support frame32 supporting the engine 11. For example, the engine support frame 32includes side frames 32 a (see FIGS. 3 and 5) located along left andright side faces of the engine 11. The engine support frame 32 includesa lower frame 32 c covering the lower side and the front side of theengine 11 and fixed to the lower portion of the side frame 32 a. The skisupport frame 31 is fixed to the front side of the engine support frame32. The structure of the engine support frame 32 and the structure ofthe ski support frame 31 are not limited to the example of snowmobile 1and may be changed.

The lower arm 43 of the snowmobile 1 is supported at a higher positionthan that of conventional snowmobiles. Specifically, as shown in FIG.2B, the proximal portions 43 a and 43 b of the lower arm 43 areconnected to the ski support frame 31 at a position higher than thelower end 11 g of the engine 11. Also, the proximal portions 43 a and 43b of the lower arm 43 are positioned higher than the rotational centerC1 of the crank shaft 11 a. In other words, the proximal portions 43 aand 43 b of the lower arm 43 are located above the horizontal plane H1passing through the rotational center C1 in side view of the vehiclebody. The horizontal plane H1 is defined as a plane parallel to skis 41Rand 41L in a state in which no load is applied to the vehicle body. “Astate in which no load is applied to the vehicle body” means a state inwhich the driver does not ride on the vehicle and only the vehicle's ownweight is applied to the vehicle body. The two proximal portions 43 aand 43 b of the lower arm 43 may be located at approximately the sameheight as the rotational center C1 of the crank shaft 11 a. That is, thehorizontal plane H1 may cross the proximal portions 43 a and 43 b of thelower arm 43 in side view of the vehicle body.

The above described layout can raise the position of the lower arm 43,while keeping the center of gravity of the driving system low. In otherwords, the center of gravity of the vehicle body is prevented frombecoming high, and running resistance can be reduced when the vehicletravels in deep snow. In some snowmobiles, the height of the center ofgravity of the drive system including the engine is located in a rangefrom the vicinity of the crank shaft of the engine to the vicinity ofthe height of the secondary shaft. In conventional snowmobiles, sincethe lower arm is connected to the vehicle frame at the almost sameheight as the lower end of the engine, the center of gravity of thedriving system and the position of the lower arm are greatly apart inthe vertical direction. Unlike conventional snowmobiles, since theproximal portions 43 a and 43 b of the lower arm 43 in the snowmobile 1are located higher than the rotational center C1 of the crank shaft 11a, the height of the lower arm 43 is closer to the height of the centerof gravity of the drive system than that in the conventionalsnowmobiles. As a result, running resistance when traveling in deep snowcan be reduced without raising the center of gravity of the vehicle bodyin the vertical direction.

As shown in FIG. 2B, in the example of snowmobile 1, the height h1 fromthe lower ends of the skis 41R and 41L to the proximal portions 43 a and43 b of the lower arm 43 is 320 mm or more in a state where no load isapplied to the vehicle body. By setting the height h1 at these levels,the position of the lower arm 43 is higher than that of the conventionalsnowmobiles, and as a result, the running resistance can be reduced whenthe vehicle travels in deep snow. The height h1 may preferably bebetween 330 mm and 550 mm.

In another example of the snowmobile, the position of the proximalportion of one of the two proximal portions 43 a and 43 b of the lowerarm 43 may be higher than the rotational center C1 of the crank shaft 11a, whereas the position of the other proximal portion may be lower thanthe rotational center C1 of the crank shaft 11 a. For example, the lowerarm 43 may be inclined such that the proximal portion 43 a of the frontrod 43 m is higher than the proximal portion 43 b of the rear rod 43 n.In that case, the proximal portion 43 a of the front rod 43 m may belocated higher than the horizontal plane H1 and the proximal portion 43b of the rear rod 43 n may be located lower than the horizontal planeH1.

In still another example of the snowmobile, a different portion from theproximal portions 43 a and 43 b of the lower arm 43 may be locatedhigher than the horizontal plane H1 in a state in which no load isapplied to the vehicle body. For example, the lower arm 43 may be curvedsuch that the middle portion in the left-right direction of the lowerarm 43 bulges upward. In this case, the highest portion of the lower arm43 may be located higher than the horizontal plane H1.

The proximal portions 43 a and 43 b of the lower arm 43 rotate about theaxis Ax1 shown in FIG. 2B. The axis Ax1 passes through a position abovethe rotational center C1 of the crank shaft 11 a. That is, theintersection point Q4 at which the axis Ax1 crosses the vertical line V2passing through the rotational center C1 is positioned higher than therotational center C1. Unlike the example of snowmobile 1, the axis Ax1may pass through the position of the rotational center C1 of the crankshaft 11 a. That is, the intersection point Q4 is positioned atapproximately the same height as the rotational center C1. The lower arm43 may be inclined such that its front portion is higher than its rearportion, and thus the axis Ax1 may be inclined relative to thehorizontal plane H1. In this case, unlike the example of snowmobile 1,the axis Ax1 may go through the position below the rotational center C1of the crank shaft 11 a.

As described above, the distal end 43 p of the lower arm 43 and thedistal end 42 p of the upper arm 42 are connected to the knuckle 44. Theplane P1 shown in FIG. 2B is an imaginary plane passing through thedistal end 43 p of the lower arm 43 and the distal end 42 p of the upperarm 42 and parallel to the vehicle width direction. As shown in FIG. 2B,the intersection point Q1 at which the plane P1 and the axis Ax1 crosseach other may be located higher than the rotational center C1 of thecrank shaft 11 a. That is, the intersection point Q1 may be locatedabove the horizontal plane H1.

As shown in FIG. 1, the vehicle frame 30 includes a belt housing 33covering the upper side of the track belt 16. The seat 8 is locatedabove the belt housing 33. The belt housing 33 includes, on the lateralsides thereof, foot rests 33 a for the driver to rest the driver's feeton. The foot rest 33 a extends rearward from the foremost portion of thebelt housing 33. As shown in FIG. 2A, the proximal portions 43 a and 43b of the lower arm 43 are located higher than the foot rest 33 a. Thispositional relationship can effectively prevent a lot of snow fromhitting the lower arm 43, if the foot rest 33 a is located at a lowposition. In the example of snowmobile 1, the lower arm 43 is locatedhigher than the foremost portion of the foot rest 33 a.

As described above, the snowmobile 1 includes a track belt drive shaft14. As shown in FIG. 2B, the proximal portions 43 a and 43 b of thelower arm 43 may be positioned higher than the rotational center of thetrack belt drive shaft 14. Further, the proximal portions 43 a and 43 bof the lower arm 43 may be located higher than the lower end of thedriving pulley 12 a of the transmission 12.

As described above, the distal end 43 p of the lower arm 43 is connectedto the knuckle 44. As shown in FIG. 2B, the distal end 43 p of the lowerarm 43 is located higher than the lower end 11 g of the engine 11 in astate where no load is applied to the vehicle body. “A state where noload is applied to the vehicle body” means, as described above, a statein which the driver does not ride on the vehicle and only the vehicle'sown weight is applied to the vehicle body. In the example of snowmobile1, the lower arm 43 is arranged substantially in parallel with thehorizontal plane in a state where no load is applied to the vehiclebody. Therefore, the distal end 43 p of the lower arm 43 is positionedhigher than the rotational center C1 of the crank shaft 11 a, similarlyto the proximal portions 43 a and 43 b. In other words, the distal end43 p of the lower arm 43 is located above the horizontal plane H1passing through the rotational center C1 of the crank shaft 11 a. Unlikethe example of snowmobile 1, the lower arm 43 may extend obliquelydownward and outwardly in the vehicle width direction from the proximalportions 43 a and 43 b in a state where no load is applied to thevehicle body. In that case, the distal end 43 p of the lower arm 43 maybe positioned below the horizontal plane H1.

In the example of snowmobile 1, the height h1 from the lower ends of theskis 41R and 41L to the proximal portions 43 a and 43 b of the lower arm43 is greater than half of the height h2 from the lower ends of the skis41R and 41L to the proximal portions 42 a and 42 b of the upper arm 42.Also, the height from the lower ends of the skis 41R and 41L to thedistal end 43 p of the lower arm 43 is larger than half of the heightfrom the lower ends of the skis 41R and 41L to the distal end 42 p ofthe upper arm 42.

In the example of snowmobile 1, similarly to the lower arm 43, the upperarm 42 is connected to the ski support frame 31 at a high position. Morespecifically, as shown in FIG. 2B, the proximal portions 42 a and 42 bof the upper arm 42 are connected to the ski support frame 31 at aposition higher than the rotational center C2 of the secondary shaft 13.That is, the proximal portions 42 a and 42 b of the upper arm 42 arepositioned above the horizontal plane H2 passing through the rotationalcenter C2 of the secondary shaft 13. The proximal portions 42 a and 42 bof the upper arm 42 are rotatable about the axis Ax2 (see FIG. 2B) sothat the upper arm 42 can move up and down about the proximal portions42 a and 42 b. The axis Ax 2 of the proximal portions 42 a and 42 bpasses through a position above the rotational center C2 of thesecondary shaft 13. That is, the intersection point Q3 at which the axisAx 2 crosses the vertical line V1 passing through the rotational centerC2 is located above the rotational center C2.

The above described location of the upper arm 42 can reduce the forceacting on the vehicle frame 30 from the knuckle 44 via the upper arm 42or prevent an increase of force. More specifically, when the skis 41Rand 41L moves up and down, the force acting on the skis 41R and 41L fromthe snow surface is transmitted to the vehicle frame 30 via the upperarm 42 and the knuckle 44. At this time, the knuckle 44 works like alever, and the connecting portion between the knuckle 44 and the lowerarm 43 words as the fulcrum of the lever. For example, when skis 41R and41L move upward, the left and right knuckles 44 tilt such that the lowerends thereof widen outwardly in the vehicle width direction because theupper arms 42 are shorter than the lower arms 43. At this time, theknuckle 44 and the vehicle frame 30 pull each other through the upperarm 42. That is, a pulling force acts between the knuckle 44 and thevehicle frame 30 via the upper arm 42. In the example of snowmobile 1,the upper arms 42 are supported at a position higher than the conventionsnowmobiles. Therefore, a sufficient distance can be ensured between thedistal end 43 p of the lower arm 43 and the distal end 42 p of the upperarm 42 in the vertical direction (as described above, the distal end 43p is the connection portion between the lower arm 43 and the knuckle 44,and the distal end 42 p is the connection portion between the upper arm42 and the knuckle 44). As a result, the lever ratio of the knuckle 44reduces, and thus the force acting on the vehicle frame 30 from theknuckle 44 via the upper arm 42 can be reduced. Alternatively, as aresult, it can be prevented that the force acting on the vehicle frame30 from the knuckle 44 via the upper arm 42 is increased due to raisingthe position of the lower arm 43.

In some snowmobiles, the height of the center of gravity of the drivesystem, including the engine, is located in the range from the vicinityof the crank shaft of the engine to the vicinity of the secondary shaft.In the example of snowmobile 1, the rotational center C2 of thesecondary shaft 13 is located lower than the axis Ax2 of the proximalportions 42 a and 42 b. Therefore, it is possible to keep the center ofgravity of the driving system at a low position. In other words, it ispossible to prevent the center of gravity of the vehicle body frombecoming high.

Unlike the example of FIG. 2B, the proximal portions 42 a and 42 b ofthe upper arm 42 may be arranged such that the axis Ax2 passes throughthe rotational center C2 of the secondary shaft 13. The two proximalportions 42 a and 42 b of the upper arm 42 may be located atapproximately the same height and the axis Ax2 may be arrangedhorizontally. In another example, the lower arm 43 may be inclined suchthat the proximal portion 43 a of the front rod 43 m is higher than theproximal portion 43 b of the rear rod 43 n. In addition, the axis Ax2may be inclined relative to the horizontal plane H2.

In the example of snowmobile 1, in a side view of the vehicle body, theheight h2 (see FIG. 2B) from the lower end of the skis 41R and 41L tothe proximal portions 42 a and 42 b of the upper arm 42 is 550 mm ormore. The height h2 is preferably 560 mm or more. In a side view of thevehicle body, the height h3 (see FIG. 2B) from the lower end 11 g of theengine 11 to the proximal portions 42 a and 42 b of the upper arm 42 is300 mm or more. The height h3 may be 350 mm or more. The height h3 maybe 380 mm or more.

As shown in FIG. 2B, in the example of snowmobile 1, the proximalportions 42 a and 42 b of the upper arm 42 are positioned higher thanthe upper end of the driven pulley 12 b. That is, the intersection pointQ3, at which the axis Ax2 crosses the vertical line V1 passing throughthe rotational center C2 of the secondary shaft 13, is located above theupper end of the driven pulley 12 b. The proximal portions 42 a and 42 bof the upper arm 42 may be located at approximately the same height asthe upper end of the driven pulley 12 b.

As described above, the distal end 42 p of the upper arm 42 is connectedto the knuckle 44. In a state where no load is applied to the vehiclebody, the position of the distal end 42 p of the upper arm 42 is higherthan the position of the rotational center C2 of the secondary shaft 13.That is, in a state where no load is applied to the vehicle body, theheight from the lower ends of the skis 41R and 41L to the distal end 42p of the upper arm 42 is greater than the height from the lower ends ofthe skis 41R and 41L to the rotational center C2 of the secondary shaft13.

FIG. 2B shows an imaginary plane P1 passing through the distal end 43 pof the lower arm 43 and the distal end 42 p of the upper arm 42 andwhere imaginary plane P1 is parallel to the vehicle width direction. Theintersection point Q2, at which the axis Ax2 passing through therotational center of the proximal portions 42 a and 42 b of the upperarm 42 crosses the imaginary plane P1, is located higher than therotational center C2 of the secondary shaft 13. That is, theintersection point Q2 is located above the horizontal plane H2.

The skis 41R and 41L are connected to the lower ends 44 f of theknuckles 44. The upper arm 42 is connected to the upper end 44 e (thefirst connecting portion) of the knuckle 44. The distance D1 (see FIG.2B) from the lower end 44 f of the knuckle 44 to the upper end 44 e is,for example, 430 mm or more. The distance D1 may be 470 mm or more. Thedistance D1 may be 500 mm or more.

In the example of snowmobile 1, the knuckle 44 includes a crossbar 44 d(second connecting portion) in a midway portion thereof in the verticaldirection. The lower arm 43 is connected to the crossbar 44 d. In theexample of snowmobile 1, the cross bar 44 d is positioned lower than themiddle position (center position) between the lower end 44 f and theupper end 44 e of the knuckle 44. In another example, the cross bar 44 dmay be located at approximately the same height as the middle positionbetween the lower end 44 f and the upper end 44 e of the knuckle 44. Instill another example, the cross bar 44 d may be located higher than themiddle position between the lower end 44 f and the upper end 44 e of theknuckle 44.

As described above, the vehicle frame 30 includes an engine supportframe 32 and a ski support frame 31. As shown in FIG. 2A, the skisupport frame 31 is located foreword of and connected to the enginesupport frame 32. In the example of snowmobile 1, the ski support frame31 is shifted upward relative to the engine support frame 32. That is,as shown in FIG. 5, the lower end 31 e at the rearmost portion of theski support frame 31 is connected to the engine support frame 32 and islocated upward from the lower end 32 f of the engine support frame 32.This allows the lower arm 43 and the upper arm 42 to be supported athigh positions.

As shown in FIG. 5, the ski support frame 31 includes, at the lowermostposition thereof, arm connecting portions 31 c and 31 d for supportingthe proximal portions 43 a and 43 b of the lower arm 43. In other words,the ski support frame 31 includes a portion located upward from thelower end 32 f of the foremost of the engine support frame 32. Theportion has the arm connecting portions 31 c and 31 d formed thereon. Asdescribed above, in the example of snowmobile 1, the ski support frame31 is composed of a plurality of panels 31 f and 31 g. The armconnecting portions 31 a and 31 b are fixed to the lowermost portion ofthe side panel 31 g. The lower end 31 e of the rearmost portion of theside panel 31 g is connected to the engine support frame 32. In anotherexample, the ski support frame 31 may be composed of a plurality ofpipes. In the other example, a pipe having the arm connecting portions31 c and 31 d formed thereon may be located upward from the lower end 32f of the engine support frame 32 and connected to the engine supportframe 32. In the example of snowmobile 1, the ski support frame 31 andthe engine support frame 32 are formed separately and are fixed to eachother by a fixing means such as welding or bolts, for example.Alternatively, the ski support frame 31 and the engine support frame 32may be integrally formed.

FIG. 2A shows a straight line L1 that is an imaginary straight lineconnecting the foremost of the proximal portion 43 a of the front rod 43m of the lower arm 43 and the lower end 11 g of the engine 11. Asdescribed above, the proximal portion 43 a of the lower arm 43 isconnected to the ski support frame 31 at a position higher than thelower end 11 g of the engine 11. Therefore, the straight line L1 isinclined relative to the horizontal plane passing through the lower end11 g of the engine 11. In the example of snowmobile 1, the angle θ1between the imaginary straight line L1 and the horizontal plane isbetween 15 degrees and 45 degrees¥ in a side view of the vehicle body.

As shown in FIG. 5, a cover member 51 is disposed under the ski supportframe 31. The cover member 51 includes a lower surface portion 51 acovering the lower side of the ski support frame 31 and extendingobliquely forward and upward. The cover member 51 prevents a lot of snowfrom hitting the lower portion of the engine support frame 32 andprevents a lot of snow from hitting the lower portion of the engine 11.In the example of snowmobile 1, the lower surface portion 51 a of thecover member 51 extends obliquely forward and upward from the lower end32 f of the foremost of the engine support frame 32.

As shown in FIG. 2A, in the example of snowmobile 1, the lower surfaceportion 51 a is curved so as to bulge downward. In a side view of thevehicle body, the distance between the lower surface portion 51 a andthe imaginary straight line L1 is the maximum D1 at the midway positionbetween the front end of the lower surface portion 51 a and the rear endof the lower surface portion 51 a.

As shown in FIG. 5, the cover member 51 includes lateral surfaceportions 51 b. The lateral surface portion 51 b extends upward in a sideview of the vehicle body from the lower surface portion 51 a and isconnected to the lower portion of the ski support frame 31. In theexample of snowmobile 1, the lateral surface portion 51 b extendsdiagonally upward from the lower surface portion 51 a toward the centerof the vehicle, in a vehicle width direction. More specifically, thelateral surface portions 51 b obliquely extend from the left and rightedges of the lower surface portion 51 a toward the lower edges of theski support frame 31. When snow falls on the lateral surface portion 51b, the snow flows downward on the lateral surface portion 51 b.Therefore, it is possible to prevent snow from collecting on the upperside of the cover member 51. The lateral surface portion 51 b may not beinclined. That is, the lateral surface portion 51 b may be arrangedvertically. In still another example, the cover member 51 does notinclude the lateral surface portion.

In the example of snowmobile 1, the cover member 51 is formed separatelyfrom the ski support frame 31 and is fixed to the ski support frame 31by a fixing means such as welding or bolts. As shown in FIG. 5, the rearedge 51 c of the lateral surface portion 51 b is connected to the enginesupport frame 32. In the example of snowmobile 1, the cover member 51 isformed separately from the engine support frame 32 and is fixed to theengine support frame 32 by a fixing means such as welding or bolts. Morespecifically, the rear edge 51 c of the lateral surface portion 51 b isfixed to the front surface of the lower frame 32 c of the engine supportframe 32. The connecting structure of the cover member 51 is not limitedto the example of snowmobile 1. For example, the cover member 51 may beintegrally formed with a member of the ski support frame 31.Alternatively, the cover member 51 may be integrally formed with amember of the engine support frame 32.

As shown in FIG. 2A, the snowmobile 1 includes suspension 45. The upperends 45 b of the suspensions 45 are connected to the ski support frame31. The suspension 45 is located between the front rod 42 m and the rearrod 42 n of the upper arm 42. The upper end 45 b of the suspension 45 islocated higher than the proximal portions 42 a and 42 b of the upper arm42. The lower end 45 a of the suspension 45 is connected to the lowerarm 43.

As shown in FIG. 2B, the upper end 45 b of the suspension 45 ispositioned higher than the rotational center C2 of the secondary shaft13. That is, the upper end 45 b of the suspension 45 is located abovethe horizontal plane H2 passing through the rotational center C2. Thisarrangement of the suspension 45 prevents the angle between thesuspension 45 and the lower arm 43 from decreasing due to raising theposition of the lower arm 43. As a result, the suspension 45 caneffectively receive the force acting on the lower arm 43 when the skis41R and 41L move up and down, and provide a suitable damping function.

As shown in FIG. 5, the ski support frame 31 includes a suspensionconnecting portion 31 f to which the upper end 45 b of the suspension 45is connected. The ski support frame 31 includes a portion protrudingupward from a portion on which the arm connecting portions 31 a, 31 b,31 c, and 31 d are formed. The protruding portion has the suspensionconnecting portion 31 f formed thereon. In the example of snowmobile 1,the ski support frame 31 includes the side panel 31 g to which the armconnecting portions 31 a, 31 b, 31 c, and 31 d are fixed. The upperportion 31 h of the ski support frame 31 further protrudes upward fromthe upper edge of the side panel 31 g. The upper portion 31 h is, forexample, a plate-like portion extending further upward from the sidepanel 31 g, and is formed integrally with the side panel 31 g. Thesuspension connecting portion 31 f is fixed to the upper portion 31 h.The structure of the ski support frame 31 is not limited to the exampleof snowmobile 1. For example, the upper portion 31 h may not be formedintegrally with the side panel 31 g. In this case, the upper portion 31h may be welded or bolted to the side panel 31 g.

As shown in FIG. 4, the ski support frame 31 includes two upper portions31 h that are located away from each other in the vehicle widthdirection (lateral direction). The left and right suspensions 45 arerespectively connected to the upper portions 31 h. A rod 31 i extends inthe vehicle width direction and is fixed to the upper portions 31 h.This rod 31 i improves the rigidity of the ski support frame 31 againstthe force acting on the ski support frame 31 from the suspensions 45.

As described above, the upper end 45 b of the suspension 45 ispositioned higher than the rotational center C2 of the secondary shaft13. In the example of snowmobile 1, the upper end 45 b of the suspension45 is located higher than the upper end of the driven pulley 12 bmounted on the secondary shaft 13. The upper end 45 b of the suspension45 is located higher than the lower end 9 a (see FIG. 1) of the fueltank 9. Further, the upper end 45 b of the suspension 45 is positionedhigher than the lower end 8 a (see FIG. 1) of the seat 8.

As shown in FIG. 4, the snowmobile 1 includes a tie rod 24 for steeringthe skis 41R and 41L. The tie rod 24 is indirectly or directly connectedto the lower end of the steering column 22. The tie rod 24 extends inthe vehicle width direction and includes tip ends 24 a (see FIG. 2A)connected to the knuckles 44. The rotation of the steering handle 21 andthe steering column 22 is transmitted to the knuckle 44 through the tierod 24. The tie rod 24 is located higher than the lower arm 43, and thetip end 24 a of the tie rod 24 is located higher than the rotationalcenter C1 of the crank shaft 11 a (see FIG. 2B).

As shown in FIG. 2A, the knuckle 44 includes a front post portion 44 aand a rear post portion 44 b. The upper end of the front post portion 44a and the upper end of the rear post portion 44 b are connected to eachother. The lower end of the front post portion 44 a and the lower end ofthe rear post portion 44 b are also connected to each other. Across bar44 d extends between and is fixed to a midway portion of the front postportion 44 a and a midway portion of the rear post portion 44 b. Thedistal end 43 p of the lower arm 43 is located above and connected tothe cross bar 44 d. The structure of the knuckle 44 is not limited tothe example shown in FIG. 2A. For example, the knuckle 44 may furtherinclude another cross bar located below the cross bar 44 d and fixed tothe front post portion 44 a and the rear post portion 44 b. The tip endof the tie rod 24 is connected to the rear post portion 44 b.

The present invention is not limited to the snowmobile 1 explainedabove, and various modifications may be made. In the example ofsnowmobile 1, the proximal portions 43 a and 43 b of the lower arm 43are located higher than the rotational center C1 of the crank shaft 11.However, the proximal portions 43 a and 43 b of the lower arm 43 can belocated lower the rotational center C1 of the crank shaft 11.

Although the present invention has been illustrated and described hereinwith reference to embodiments and specific examples thereof, it will bereadily apparent to those of ordinary skill in the art that otherembodiments and examples may perform similar functions and/or achievelike results. All such equivalent embodiments and examples are withinthe spirit and scope of the present invention, are contemplated thereby,and are intended to be covered by the following claims.

What is claimed is:
 1. A snowmobile comprising: a vehicle frame, wherein the vehicle frame comprises a ski support frame in a front portion of the vehicle frame; a ski disposed outwardly in a vehicle width direction from the ski support frame; a knuckle with a lower end having the ski connected thereto; an upper arm with a proximal portion connected to the ski support frame, the upper arm extending outwardly in the vehicle width direction from the proximal portion to connect to the knuckle, the proximal portion being rotatable so that the ski and the knuckle can move up and down relative to the ski support frame; a lower arm disposed below the upper arm with a proximal portion connected to the ski support frame, and extending outwardly in the vehicle width direction from the proximal portion to connect to the knuckle, the proximal portion being rotatable so that the ski and the knuckle can move up and down relative to the ski support frame; and a drive system, wherein the drive system comprises an engine and a secondary shaft, the engine being disposed rearward of the ski support frame and comprising a crank shaft, the secondary shaft being located higher than the crank shaft and configured to receive a drive force from the crank shaft, wherein the proximal portion of the upper arm has a rotational center and an axis passing through the rotational center, and wherein the axis goes through a position of a rotational center of the secondary shaft in a side view of a vehicle body, or through a position above the rotational center of the secondary shaft in the side view of the vehicle body.
 2. The snowmobile according to claim 1, wherein at least a portion of the proximal portion of the upper arm is positioned higher than the rotational center of the secondary shaft.
 3. The snowmobile according to claim 1, wherein each of the upper arm and the lower arm comprises a distal end connected to the knuckle, and wherein an intersection point, at which the axis passing through the rotational center of the proximal portion of the upper arm crosses an imaginary plane, is located higher than the rotational center of the secondary shaft, where the imaginary plane is a plane that passes through the distal ends of the lower arm and the upper arm and is parallel to the vehicle width direction.
 4. The snowmobile according to claim 1, wherein the upper arm comprises a distal end connected to the knuckle, and the height from a lower end of the ski to the distal end of the upper arm is greater than the height from the lower end of the ski to the rotational center of the secondary shaft.
 5. The snowmobile according to claim 1, wherein the knuckle comprises a first connecting portion having the upper arm connected thereto and a second connecting portion having the lower arm connected thereto, and the second connecting portion is located at substantially the same height as a middle position between the first connecting portion and the lower end of the knuckle or located lower than the middle position.
 6. The snowmobile according to claim 1, wherein the proximal portion of the lower arm is located higher than a rotational center of the crank shaft of the engine.
 7. The snowmobile according to claim 1, further comprising a suspension with an upper end connected to the ski support frame and a lower end connected to the lower arm, wherein the upper end of the suspension is located higher than the rotational center of the secondary shaft.
 8. The snowmobile according to claim 1, wherein the vehicle frame comprises an engine support frame supporting the engine, and the ski support frame is shifted upward relative to the engine support frame. 